The purpose of this project is to study the reversal of preneoplastic bladder lesions by retinoids (vitamin A and its analogs) in organ culture. Areas of specific interest include (1) the effects of retinoids on in vitro induced hyperplasia and dysplasia; (2) the effects of retinoids on in vivo carcinogen-induced hyperplasia and dysplasia; and (3) the functional relationships between retinoids and glucocorticoids.